Producing alcohols and/or ketones from alkanes and other co-reactants is known. Often, such technology is pursued in attempts to discover viable processes for making useful chemicals directly from hydrocarbons, anticipating dwindling petrochemical feedstocks. In other instances, the co-reactant may be a by-product from another process, and an economical way of converting the by-product to a useful material may be needed. Sometimes a particular kind of alcohol or ketone, or mixture of alcohols and/or ketones is desired.
A number of publications provide a useful background in this technology. For example, A. N. Bashikirov, et al., in "Synthesis of Higher Aliphatic Alcohols by Direct Oxidation of Paraffinic Hydrocarbons," Proc. World Pet. Cong., Vol. 4, (1959) pp. 175-183, report the "directed" synthesis of higher aliphatic alcohols via the liquid-phase oxidation of paraffinic hydrocarbons in the presence of boric acid, and by the selection of proper operating conditions which include a low oxygen concentration. Apparently, the boric acid serves as an esterification agent in the oxidation, and the conversion of alcohols into boric acid esters prevents them from further oxidation by interrupting the oxidative conversion chain at the alcohol stage. See also N. J. Stevens, et al., "A New Route for Alcohols," Chemical Engineering Progress, Vol. 64, No. 7, (1968) p. 61-66. Similarly, U.S. Pat. No. 3,243,449 teaches the oxidation of saturated hydrocarbons having 4 to 8 carbon atoms with molecular oxygen in the presence of metaboric acid or a less hydrated form of orthoboric acid, including boric anhydride, to produce borate esters. In this process, the contact temperature for the reactants is in the range of about 140.degree. to 180.degree. C., and the reaction is maintained so that the partial pressure of water in the exit gases, i.e., the vapor above the liquid reaction mixture, in psia is not greater than P, where P is given by the expression log.sub.10 P=0.01112T-0.259.
In this same area is wOrk reported by M. J. ljam, et al., in "Liquid-Phase Oxidation of n-Dodecane in the Presence of Boron Compounds," Ind. Eng. Chem. Prod. Res. Dev., Vol. 20, (1981) pp. 315-319. The paper describes experiments on the production of neutral oxidation products rich in alcohols by the direct air oxidation of n-dodecane in the presence of boron compounds, such as tributoxyboroxine, boron trioxide, dibutoxyborane, etc. As with some of the previously discussed publications, lean oxygen-nitrogen mixtures (4% oxygen) are also used, here giving a mixture of six possible straight-chain C.sub.12 alcohols.
In the absence of boric or other like catalysts, the direct oxidation of hydrocarbons produces alcohols and ketones in usually less than 60% selectivity, even at conversions of 20-30%. In the presence of boric acid, the selectivity to alcohols is increased to about 75-80% at 20-30% conversion, but even here, there are carboxylic acids and other by-products produced. In addition, the hydrolysis of the borate esters and isolation of the products is not a simple operation.
Paraffins having four to eight carbon atoms may be oxidized in the liquid phase with molecular oxygen in a reactor in which the manganese content is maintained in the range of 2 to 50 ppm to produce carboxylic acids, according to U.S. Pat. No. 3,859,346. The manganese may be in the form of manganese salts of carboxylic acids, e.g. manganese naphthenate, or in an aqueous solution, e.g. manganese acetate.
Also of general interest is Porphyrin Catalysts for Olefin Epoxidation: A literature review 1985-86," Catalysts in Chemistry, Vol. 21, No. 3, (1987) pp. 106-112. A number of oxidation processes are briefly mentioned, including ones involving iron and manganese porphyrin catalysts, primarily with a concentration on processes producing epoxides. The oxidation of cyclohexane to cyclohexanol and cyclohexanone by molecular oxygen catalyzed by ruthenium (III)-ethylenediaminetetraacetic acid in the presence and absence of the micelle cetyltrimethylammonium bromide (CTAB) is reported by M. M. Taqui Kahn, et al. in "Ru(III)-EDTA Catalyzed Oxidation of Cyclohexane by Molecular Oxygen," Journal of Molecular Catalysis, Vol. 45, (1988) pp. 51-56. The rate of oxidation was found to increase in the presence of CTAB. Similarly of interest is T. Lau, et al., "Ruthenium Catalysed Oxidation of Alkanes with Alkylhydroperoxides," J. Chem. Soc., Chem. Commun., (1988) pp. 1406-1407, which reports that cis-[Ru(II)(L).sub.2 (OH.sub.2).sub.2 ].sup.2+ complexes may catalyze the oxidation of saturated hydrocarbons, such as cyclohexane, hexane and heptane, to alcohols and ketones by t-butylhydroperoxide. The L in the ruthenium catalyst formula may be substituted 2,2'-bipyridines of 1,10-phenanthrolines.
Of somewhat more pertinent interest are a number of publications describing research focussing on metalloporphyrin catalysts to make alcohols and ketones. For example, D. Mansuy, et al. in Metalloporphyrin-Catalyzed Hydroxylation of Cyclohexane by Alkyl Hydroperoxides: Pronounced Efficiency of Iron-Porphyrins," Angew. Chem. Int. Ed. Engl., Vol 19, No. 11, (1980) pp. 909-910, describe the catalyzed hydroxylation of nonactivated alkanes, either by molecular oxygen in the presence of a reducing agent, or by two-electron oxidants. The researchers noted that the metalloporphyrins studied fell into three classes. First, the Cu(II)-, Ni(II)-, Zn(II)-, Mg(II)-, V(IV)- and Ti(IV)-porphyrins were found to be completely inactive under the reaction conditions used. The Co(TPP) and Os(TPP)(CO)(PY) compounds were found to catalyze cyclohexane oxidation, the former giving even a slightly faster reaction and better yields than Fe(TPP)(Cl), but both showing decreasing activity over time. The third group of Fe- and Mn(TPP)Cl were found to be true catalysts. A related study is reported in D. Mansuy, et al., Alkane Hydroxylation Catalyzed by Metalloporphyrins: Evidence for Different Active Oxygen Species with Alkylhydroperoxides and Iodosobenzene as Oxidants," Tetrahedron Letters, Vol. 23, No. 27, (1982) pp. 2781-2784. The comparative examination of cyclohexane and n-heptane hydroxylations by cumylhydroperoxide and iodosobenzene, catalyzed by various metalloporphyrins, indicated that different active oxygen species, presumably the cumyloxy radical and a metal-oxo intermediate were involved in these reactions. The metals used in the catalysts included iron, manganese, cobalt, rhodium and chromium.
Azido(tetraphenylporphyrinato) complexes of Cr.sup.III, Mn.sup.III and Fe.sup.III are found to catalyze the selective, low temperature hydroxylation of isobutane with molecular oxygen, according to P. E. Ellis, et al. in "Effect of Axial Azide on the Selective, Low Temperature Metalloporphyrin-catalysed Reactions of Isobutane with Molecular Oxygen," J. Chem. Soc., Chem. Commun., 1989, pp. 1187-88.
P.H.J. Carlsen in "Ruthenium Catalyzed Oxidation of Alkanes," Synthetic Communications, Vol. 17, No. 1, (1987) pp. 19-23 reports the use of a RuCl.sub.3 catalyst in a solvent system containing CCl.sub.4 -CH.sub.3 CN-H.sub.2 O and using sodium metaperiodate as the stoichiometric oxidation agent to oxidize a series of alkyl substituted alkanes. Norbornane and bicyclo[2.2.2]octane are oxidized to the corresponding ketone and adamantane is transformed to 1-adamantol. Another article of interest is Y.V. Geletti, et al., "Oxidation of Saturated Hydrocarbons by Hydrogen Peroxide in Pyridine Solution Catalysed by Copper and Iron Perchlorates," J. Chem. Soc., Chem. Comm., (1988) pp. 936-937. The hydrocarbons used are cyclohexane and 2-methylbutane, which yield the ketone and alcohol with alkyl radicals not being intermediates.
Additionally of note is U.S. Pat. No. 4,459,427 which teaches that a mixture of the alcohol and ketone derivatives of alkanes may be produced by reacting the alkane with a hydrocarbyl hydroperoxide, e.g. t-butyl hydroperoxide in the presence of a catalyst. The catalyst may be an iron or manganese square planar complex having heterocyclic nitrogen-donor ligands, e.g. a porphyrin or phthalocyanine complex, which complex has either no axial ligands, for example, the lower valency or cationic complex, or an axial ligand which is non-coordinating or weakly-coordinating. Weakly coordinating ligands are defined as ligands having a coordinating power less than that of the chloride anion. The alkane employed is preferably a linear or branched alkane having from about 2 to 20 carbon atoms. Suitable complexes having no axial ligands are either neutral iron (II) and manganese (II) complexes, e.g. Fe(II)(TPP) and Mh(II)(TPP) or iron (III) and manganese (III) cationic complexes, such as [Fe(III)(TPP)].sup.+ and [Mn(III)(TPP)].sup.+.
Finally, European Patent Application 0274909 A2 is of interest. It submits that hydrocarbons, particularly lower molecular weight alkanes and cycloalkanes, may be oxidized with air or oxygen to form products such as alcohols, ketones and the like selectively in high yields when there is employed as the catalyst a highly active azide- or nitride-activated metal coordination complex having the structure: ##STR1## where M is a transition metal; the circle represents a ligand, and R is azide or nitride. Certain dimeric forms of these catalysts may also be employed. It is also discussed that Group IV through VIII transition metal nitrides are also effective oxidation catalysts for lower molecular weight hydrocarbons, such as alkanes. The discussion therein is also directed to certain novel azide-activated metal coordination complex catalysts, per se.
It will be appreciated that in the processes briefly described above, a wide variety of products is often achieved. In many of the reports on those processes, it was stated that a mixture of all possible products resulted. Thus, it would be advantageous if processes could be developed which would maximize the yield to a particularly useful product, in turn, by minimizing the yield to the other by-products. It would also be preferred that the reaction be able to be run at ambient temperature with catalysts that are readily obtainable so that the synthesis might be relatively simple and economical.